Interesting, although it sounds like a tedious excavation.
They found an area of shelter here that they're using for the sharing of meat, for the butchering of animals and for making flint tools and also burning material, potentially bone.
I don't believe bone would be considered a "burning material". One might discard bones into a wood fire.... which might have the added benefit of removing smells from the bones, or perhaps it is a sign of cooking. Oils in the longbones as well as cartilage might burn a little, but wouldn't be my choice for a burning material.